A reader of The NEWS wrote a letter a while ago that raised some questions about soldering. In part the writer said:
I have read many articles and most say that copper lines must be soldered with silver-based compounds or low temperature brazed with copper-based compounds. Due to the high melting point of these soldering/brazing compounds, the lines must be purged with inert gases (such as nitrogen) to prevent oxides forming in the tubing. All of the above makes sense except: If jointing tubing can be accomplished at lower temperatures, the need for high heat and nitrogen purging can be eliminated. This seems like an important advantage (if the quality of the joint can be assured). What if low temperature soldering could do the job? What if for the mass-produced products, joining of plumbing could be accomplished in a low-temperature furnace (say 500 degrees F)? I've even read reports of refrigeration technicians admitting to soft soldering joints to save costs."